The present invention relates to electrical power outlets and cigar lighter outlets, and in particular, to electrical power outlets and cigar lighter outlets, receptacles or sockets for use in automotive applications. More particularly, the present invention is related to a compact protection device for automotive cigar lighter sockets and electrical power outlets and provides protection against overheating and over-current conditions.
The trend in automotive design is for increased use of electronic devices that require more power and draw higher currents from the power outlets or cigar lighter sockets in motor vehicles.
Two common issues result. One is over-current, that is, excessive current draw due to excessive power consumption or a short circuit in the plugged-in device. Another is overheating due to high current and often poor quality of after-market accessory plugs that cannot handle the currents drawn through them.
In the past, over-current protection has been provided by using a fuse that is installed in the vehicle fuse box. This fuse is accessible to the vehicle operator and often times, such vehicle operators are inexperienced, particularly with electrical matters and may replace a blown fuse with a fuse of the wrong type, for example, a higher current fuse which will no longer provide proper over-current protection, leading to excessive current draw which can damage the vehicle wiring and/or the accessory device and, in a worst case, cause a fire or injury.
Over-temperature or overheating protection has been provided in cigar lighters in automotive vehicles typically by providing a second bimetallic element, in addition to the bimetallic thermostatic element that disconnects the cigar lighter from the electrical current when it has been heated to ignition temperature. Typically, the additional bimetallic thermostatic element responds to excessive heating and short-circuits the power to the cigar lighter socket in the vehicle, which then blows the fuse provided in the vehicle fuse box. Such over-temperature protection for vehicle cigar lighters operates adequately when the heat build-up is fast but does not adequately operate for cigar lighters when they are used as power outlets in which the heat build-up is much slower. In such case, the additional bimetallic element will fail to provide short-circuit protection.
For power outlets in automotive vehicles that are not equipped as cigar lighter outlets, typically over-temperature protection has not been provided.